Cardiac enzymes are blood tests that do not require fasting and can be done at any time of the day. The results are usually available the same day, or 30 minutes to 2 hours if the test is urgent. Myocardial enzymes reflect the degree of damage to the heart muscle. If the heart muscle is damaged or necrotic, it can cause myocardial enzymes to be released into the bloodstream, resulting in an increase in the level of myocardial enzymes in the blood. Myocardial enzyme tests are mainly used to determine if the disease is cardiac in nature, such as coronary artery disease and myocarditis. Among the commonly used indicators are lactate dehydrogenase (normal reference value is 100-240 IU/L) and creatine kinase isoenzyme (normal reference value is 0-25 IU/L). The levels of these enzymes in the blood are checked to determine if one has a heart-related condition. If middle-aged or older men suddenly experience chest pain and tightness with activity, accompanied by shortness of breath, general weakness or even discomfort in the back or gums, the level of cardiac enzymes in the blood should be checked to rule out or confirm the diagnosis of coronary artery disease.